High-concentration polyaluminum chloride: Preparation and effects of the Al concentration on the distribution and transformation of Al species

Using an instantaneous base-feeding method and a batch-feeding method, high-concentration polyaluminum chloride (PACl) products were prepared employing CaO as the basification reagent. The distribution and transformation of the Al species of PACl was explored for the first time over a broad total Al concentration (AlT) range. There is always an optimal basicity (B value) at which the product has the highest Alb content, whether AlT is high or low. The optimal B value and the highest Alb content obtained both decrease with increasing AlT. When the B value is lower than optimal, the overall reaction mainly leads to the production of Alb; when the B value is higher, the reaction leads to the production of Alc. During the dilution process, high B value PACl has a tendency towards Alb formation, while low B value PACl favors Alc formation. The transformation behaviors of Al species are influenced by AlT in the preparation or dilution process.